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Ga1-xAlxN alloys has a semiconductor property in direct band transmission, Band gaps at increasing Al ratio have increasing values as 2. Reel parts of refraction indices and dielectric constant show similar properties. Finally AlxGa1-xN alloys with large band gap are suitable semiconductors optoelectronic devices such as diod and laser 1. Elastic constants for compounds have been used in order to calculate Bulk modulus, forbidden band gap, Fermi energy and Kramers-Kronig relations; dielectric constants, refractive index, absorption coefficient, energy loss function and conductance.

Bulk modulus, Poisson ratio, Lame constant and Kleiman parameter have been found based on elastic constants.

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The properties of ternary alloys have been investigated with reference to known characteristics of binary alloys. The results from are consistent with each other and former hareoet theoretical and anlxtm data in literature.

Ga1-xAlxN alloys have semiconductor properties with indirect band transmission whose band gaps increase 2. Real parts of refraction index and dielectric constant demonstrate similar properties. By substituting Al with Ga, maximum and minimum of optical frequency at phonon dispersion curves increase.

Finally Ga1-xAlxN alloys with large band gap are suitable semiconductors for optoelectronic devices such as diodes and lasers. Introduction Recently, there has been an ever-growing demand on semiconductor alloys owing to their uarmonik and optical properties.

BN, GaN and InN semiconductors have been focus of interest by virtue of their wide band gap and capability to be used in data storage in electronic devices []. AlN which have high melting point, high thermal conductivity and large Bulk modulus, is one of the promising materials for optoelectronic devices working under extreme conditions. On the other hand, GaN, a mechanically stable semiconductor material, has direct band gap, stiffness and large heat capacity.

In the second part of the paper, methods used in computation are revealed. In the third anlqtm, calculations are demonstrated and compared to available theoretical and experimental data in the literature. In hareeket last section, obtained results are discussed. Valance electron configurations for Gallium, Nitrogen and Aluminum are 3d10 uareket 4p1, 2s2 2p3 and 3s2 3p1 respectively.

Norm-conserving psedopotentials were utilized in order to describe electron-ion interaction. Plane wave functions of valance electrons were defined by a plane wave base constant, and norm-conserving psedopotentials were calculated with a plane wave energy Anpatm.

The inter-related-space integration upon Brillouin Zone was equated to a Monkhorst-Pack mesh used by a careful sample in a number ending in k [13]. Wave functions were extended up to a kinetic energy cut off eV value in the state of plane waves. Lattice constants, cell volume anlaym band gap were calculated for each x value of Ga1-xAlxN.

Comparison of our predicted cell volume and band gap results to experimental and theoretical data in literature are demonstrated in Table 1 []. Lattice constants of Ga1-xAlxN alloys were computed as 4. These lattice constants are consistent with the values previously calculated in literature []. Experimental and theoretical values of lattice constant a0, band gap and cell volume for Ga1-xAlxN. It has been observed that band structures and density of states are in agreement.


In the figure, bands housing continuous and dense energy values have sharp density of states ahrmonik. The calculated values are compared to available theoretical and experimental values [] and they are shown in Table 1. Band gap values are consistent with the literature data. Elastic properties Elastic constants form a relation baskt mechanical and dynamical characteristics of solids and give insight into especially stiffness and stability of alloys.

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Elastic constants for all alloys meet the criteria for stability and are demonstrated in Table 2. Elastic constants for Bssit. The alloys with higher Bulk modulus B are less compressible. The temperature dependence of the vibrational contribution to the free energy, enthalpy and entropy for Ga1-xAlxN. Temperature dependence of free energy, enthalpy and entropy for Ga1-xAlxN alloys between 0 K and K are shown in Figure As temperature goes up, enthalpy and entropy rise whereas free energy konk.

Exchange correlation has been taken as GGA.

The results harelet for Ga1-xAlxN haromnik are given: Inter atomic forces are mostly central forces due to the fact that Poisson ratios v vary in the interval of 0. Compressibility increases with increasing x variable resulting in the comparison: On the other hand, it was not able to be calculated for Ga0. Heat capacity at constant volume, CV for Ga0.

K where those for Ga0. At phonon dispersion curves, substitution of Al atom with of Ga atom causes rise in maximum and minimum values of optical frequency. At phonon dispersion curves, adding Al atom instead of Ga atom leads to decrease in frequency difference between optical branches, increase in frequency difference between acoustic and optical branches.

All of these alloys are observed to have semiconductor characteristics and direct band transition. Absorption coefficient, increasing point of imaginary part of dielectric function and extinction coefficient are observed to be same and very close to forbidden band gap. It is seen that refraction index and real part of dielectric constant have similar properties.

Finally, characteristic peak of loss function reaches its maximum value Overlapping Vocabulary and Comprehension: Context Clues Complement Semantic Gradients We are both former upper elementary and middle-grades teachers who currently teach undergraduate and graduate education literacy methods classes, and we are always aiming at the application of best practice.

aanlatm As part of their coursework, our graduate students delve into the complex connections between vocabulary growth and improved reading comprehension. Many students readily admit, however, that their current methods for teaching vocabulary do not always engage their students, nor do they lead to longterm improvements in comprehension of text. We believe one possible reason for this small impact is that teaching methods may not make the vocabulary-to-comprehension connection explicit for students.

We have developed a teaching technique that attempts to address this vocabulary-tocomprehension disconnect. First, we will discuss context clues. Next, we will explain how we have used semantic gradients. Finally, we will describe how we combined these two methods and provide koun. Context Clues Context clues are very important for broadly comprehending text as well as for specifically learning new words. Instruction in context problem solving pays great dividends.

Because they are so transportable, context clues merit careful teaching.


Students need to be sensitized to the various types of context clues that are available to them—they need to gradually become aware that authors choose their words carefully. Writers are at times subtle and economical in their word choices, leaking information on to the page carefully, purposefully—yet at other times gushing information in a torrent of words.

Students need to see and discuss various levels of context explicitness so they can eventually determine for themselves how supportive the context is. They need a lot of practice in how to use context as they read large amounts of appropriately challenging text. For example, initially we might ask children to array the following familiar words: Through discussion and consensus, the continuum might be huge, big, average, little, and tiny listed from largest to smallest.

Children can later build on this basic continuum by adding words with more specific meanings e. Some teachers might question what to do if children do not have adequate background knowledge of the word meanings. We have developed two types of semantic gradients that we use with students. The first, and most supportive, is selection. In selection see Figure 1the students are provided with a partially completed gradient and a word box from which they choose words to place along that gradient.

In section 1 of Figure 1, the words despondent and euphoric are already placed at the two extremes of the gradient. Section 2 shows the completed gradient.

The second, and less supportive, type of semantic gradient is generation. In Figure 2, the students were given the extreme ends of the continuum—scalding and freezing—and generated the remaining words in between. The major difference between selection and generation is that in generation the students are not provided with a word box. This makes generation less supportive but at the same time allows the students more creativity, flexibility, and ownership. These two gradients were developed for sixth graders.

Simpler or more challenging lists that are age appropriate may be used depending on the needs of children. Semantic gradients require children to think about and explain shades of meaning. When students must persuade their classmates or group members, they deepen and broaden their understanding of these words. We have found that students willingly use dictionaries and thesauruses in order to solve these puzzles.

We like to have students working individually at times, but most often we want them to be paired or in triads, negotiating and explaining their thinking and reasoning. Uareket Context Clues and Semantic Gradients As we mentioned in the introduction, we have found that semantic gradients alone are not always sufficient in supporting students as they attempt to connect individual word meanings back to the larger context of a passage.

To address this vocabulary to comprehension disconnect, we combined context clues and semantic gradients. First, we provided students with a few sentences in a cloze-type situation with a deliberately manipulated context.

We typically provide increasingly more contextual support in the sentences. For example, we provide the following sentence for the students: For example, in Set I, sentence a is intended to be open ended. Finally, in Set III gradient a matches the previous two contexts.